Bis-amidines

ABSTRACT

Symmetrical bis-amidine derivatives of mitomycin C may be converted to unsymmetrical bis-amidine analogs by reaction with secondary amines. The compounds are active anti-tumor agents in experimental animal tumors.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of our copending applicationSer. No. 492,903 filed May 9, 1983 which in turn is acontinuation-in-part of application Ser. No. 385,149 filed June 4, 1982.The former is now U.S. Pat. No. 4,487,769, and the latter has beenabandoned.

FIELD OF THE INVENTION

The present invention refers to mitomycin analogs containing twodifferent amidino groups (Class 260 Subclass 326.24). These compoundsare mitomycin C derivatives in which both the quinone amino group andthe carbamido nitrogen atom are incorporated within an amidinosubstituent. These compounds are active antitumor substances againstexperimental animal tumors.

Nomenclature.--The systematic Chemical Abstracts name for mitomycin Cis:

[1aR-(1a,α,8α,8a,β,8b,α)]-6-amino-8-[((aminocarbonyl)oxy)methyl]-1,1a,2,8,8a,8b-hexahydro-8a-methoxy-5-methyl-azirino[2',3',3,4]-pyrrolo[1,2-a]indole-4,7-dione

according to which the azirinopyrroloindole ring system is numbered asfollows: ##STR1##

A trivial system of nomenclature which has found wide in the mitomycinliterature identifies the foregoing ring system including several of thecharacteristic substituents of the mitamycins as mitosane. ##STR2##While this system is convenient and appropriate for a number of simplederivatives such as those bearing N-substituents on the azirino ringnitrogen atom or in the 7- or 9a-positions, it suffers from certainambiguities and shortcomings for general use. With regard to thecompounds of the present invention some of which have substituents onboth the azirino ring nitrogen atom and on the side chain carbamoylnitrogen atom, there is no conventional numbering to distinguish thesepositions. Therefore, we have chosen in the present specification torefer to the azirino nitrogen atom as N^(1a) and the carbamoyl nitrogenatom as N¹⁰ in using the mitosane nomenclature system. As to thestereochemical configuration of the products of this invention, it isintended when identifying them by the root name "mitosane" or bystructural formula to identify the stereochemical configuration thereofas the same as that of mitomycin C.

DESCRIPTION OF THE PRIOR ART

Mitomycin C is an antibiotic which is produced by fermentation and ispresently on sale under Food and Drug Administration approval in thetherapy of disseminated adenocarcinoma of the stomach or pancreas inproven combinations with other approved chemotherapeutic agents and aspalliative treatment when other modalities have failed (Mutamycin®Bristol Laboratories, Syracuse, N.Y. 13201, Physician's Desk Reference35th Edition, 1981, pp. 717 and 718). Mitomycin C and its production byfermentation are the subjects of U.S. Pat. No. 3,660,578 patented May 2,1972 claiming priority from earlier applications including anapplication filed in Japan on Apr. 6, 1957.

The structures of mitomycins A, B, C, and of porfiromycin were firstpublished by J. S. Webb et al. of Lederle Laboratories Division AmericanCyanamid Company, J. Amer. Chem. Soc. 94, 3185-3187 (1962).

Recently Shirahata et al., J. Am. Chem. Soc. 1983, 105, 7199-7200 havepublished convincing evidence as to the absolute configuration ofmitomycin C on the basis of X-ray analysis of the N^(1a) -p-bromobenzoylderivative thereof. The revised absolute configuration of mitomycin C isas shown in the following formula ##STR3##

SUMMARY OF THE INVENTION

The present invention is concerned with a group of bis-amidino analogsof mitomycin C in which both the 7-amino nitrogen atom and the N¹⁰-carbamoyl nitrogen atom are part of an amidino substituent. The twoamidino groups of these bis-amidino compounds are different. Processesfor the preparation of these compounds are included in the presentinvention. The compounds of the present invention conform to structuralFormula I, which also includes compounds wherein the 7-amino nitrogenatom is incorporated within an amidino group, and the N¹⁰ -carbamoylnitrogen atom is substituted by formyl.

The compounds of Formula I have utility as antitumor agents in that theyinhibit the growth of malignant tumors in experimental animals. For thispurpose they are administered systemically to a mammal bearing a tumorin a substantially non-toxic antitumor effective dose. The parenteralroutes such as the intravenous route of administration are preferred.Disclosed herein are data comparing the present substances in vivo invarious experimental animal tumor models with mitomycin C. Based uponthese data the appropriate doses of the present substances can beestimated relative to the doses to mitomycin C employed in the treatmentof various tumors. The compounds of Formula I are also antibioticseffective against Gram+ and Gram- bacteria. ##STR4## In Formula I, R¹ ishydrogen, lower alkyl, lower alkanoyl, benzoyl or substituted benzoylwherein said substituent is lower alkyl, lower alkoxy, halo, amino, ornitro,

A and B are different and are independently selected from the grouphaving the formula ##STR5## wherein R² is hydrogen, lower alkyl, phenyl,lower alkylphenyl, lower alkoxyphenyl, halophenyl, or aminophenyl,

R³ is lower alkyl, or lower alkoxy,

R⁴ is lower alkyl, or

R³ and R⁴ together with the nitrogen atom to which they are attachedconstitute pyrrolidine, 2-, or 3-lower alkylpyrrolidine, piperidine, 2-,3-, or 4-lower alkylpiperidine, 2,6-dilower alkylpiperidine, piprazine,4-substituted piperazine wherein said 4-substituent is alkyl, orcarbalkoxy each having 1 to 8 carbon atoms, phenyl, methylphenyl,methoxyphenyl, halophenyl, nitrophenyl, or benzyl, azepine, 2-, 3-, 4-,or 5-lower alkylazepine, morpholine, thiomorpholine,thiomorpholine-1-oxide, or thiomorpholine-1,1-dioxide, or

B is the amino formyl group.

DETAILED DESCRIPTION OF THE INVENTION

In application Ser. No. 492,903 (U.S. Pat. No. 4,487,769) it wasdisclosed that treatment of bis-amidino compound similar to Formula Iabove in which A and B are each a dimethylaminomethyleneamino group witha primary amine in anhydrous methanol yielded a mitomycin C derivativesimilar to Formula I above in which A is a mono-substituted amino groupcorresponding to the amine reactant and B is the NH₂ group. Certainprimary amines when employed in that process produce compounds similarto Formula I in which A is the amidino group of the starting materialand B is the unsubstituted amino group. In other words, certain primaryamines were capable of cleaving the N¹⁰ -amidino group, but not the N⁷-amidino group of the compounds similar to Formula I in which A and Bare identical amidino groups. We have now found that secondary aminesreact with such bis-amidino compounds to replace the amino portion ofthe B substituent with the amino group corresponding to the secondaryamine used in the process. The following equation is illustrative.##STR6##

In the following equation R¹, R², R³, and R⁴ have the definitions givenabove. R^(3') and R^(4') are also defined by the same group of termsused to define R³ and R⁴, but R^(3') and R^(4') represent differentspecies with respect to R³ and R⁴ in any specific example.

The foregoing process is referred to as the amine exchange method.Substantially, any secondary amine may be employed in the processincluding alicyclic, cyclic, heteroalicyclic, and heteroaromaticsecondary amines with the proviso that they contain no functionalsubstituents which are sterically or chemically incompatible with thereaction conditions. Secondary amines having interfering functionalgroups may be employed if the functional group is derivatized by aconventional protecting group which may be removed after completion ofthe reaction. A variety of protecting groups and methods for theirremoval are known for groups such as hydroxyl, amino, and carboxyl. Itis preferred that the carbon atoms attached to the nitrogen atom of thesecondary amine reactant be methyl, methylene (--CH₂ --), or methyne(--CH═) carbon atoms. Diisopropylamine has, for example, been found tobe non-reactive in the process.

An ahydrous liquid organic compound is employed as reaction medium andany such substance may be employed so long as it is stable andsubstantially nonreactive to the reactants at the reaction temperature,and does not participate in the reaction in any other deleterious way.Anhydrous methanol is the preferred reaction medium, but other mediasuch as chloroform, methylene chloride, or other lower haloalkanes andalkanols may be employed. A reaction temperature in the range of fromabout -15° C. to about +50° C. is preferred. An excess of the aminereactant is preferably employed. By this is meant more than onemolecular proportion relative to the bis-amidino mitomycin C derivativeused as reactant.

The amide acetal method of Ser. No. 492,903 (U.S. Pat. No. 4,487,769) isalso applicable to the preparation of the present compounds by using acompound of the following formula as reactant with the amide acetalaccording to the method of our prior application. ##STR7##

In the foregoing formula R¹ and A have the same meaning as given above.The entire disclosure of our prior application Ser. No. 492,903 isincorporated herein by reference and including particularly thediscussion with respect to the amide acetal method and theidentification of various amide acetals that may be employed in theprocess. More particularly, amide acetals having the following formulaare employed. ##STR8## wherein R², R³ and R⁴ have the definitions givenwith respect to B in Claim 1 and R⁸ is independently lower alkyl, orcycloalkyl having up to 6 carbon atoms or together they are alkyleneforming with the attached oxygen atoms and intervening carbon atom acyclic structure having 5 or 6 ring members in solution in an anhydrousreaction compatible liquid organic reaction medium at 40° C. to 65° C.until the desired reaction product is formed.

In each of the foregoing processes it is desirable to monitor the courseof the reaction by thin layer chromatography by means of which thestarting material and product can be distinguished. The optimum reactiontime is judged on the basis of disappearance of starting material,appearance of product, or a combination of each particularly in thoseinstances wherein decomposition is a competing reaction.

SPECIFIC EMBODIMENTS

General Procedure:

Amine Exchange Method: This method involves reaction of the symmetricalbis-amidino mitosane e.g.: Formula I wherein A and B are identical, withan excess of a secondary amine in anhydrous methanol at ambienttemperature. Where possible, the progress of the reaction is monitoredby thin layer chromatography. The reaction is terminated by evaporatingthe solvent and excess reagent under reduced pressure followed byremoving the last traces under high vacuum. The resulting syrupymaterial is subsequently chromatographed to obtain the desiredunsymmetrical bis-amidino mitosane which is then fully characterized.Flash chromatography on silica is appropriate, but when the conventionalgravity flow method on a silica gel column is employed, degradation tothe N¹⁰ -formyl compound sometimes occurs as is discussed more fullybelow.

Formamide Acetal Method: This method involves reaction of a 7-amidinomitosane e.g.: a compound similar to Formula I wherein B is NH₂ with anappropriate substituted formamide acetal in a methanol-chloroformmixture at ca. 55° C. for up to 72 hours. The progress of reaction ismonitored by thin layer chromatography. After the reaction is complete,the reaction mixture is worked up in a similar manner to the above, andpure bis-amidine is obtained after neutral alumina columnchromatography.

EXAMPLE 1 7-[(Dimethylamino)methylene]amino-N¹⁰-(4-morpholinyl)methylene-9a-methoxymitosane ##STR9##

To a solution of 7-[(dimethylamino)methylene]amino-N¹⁰-(dimethylamino)methylene-9a-methoxymitosane (485 mg, 1.09 mM) isanhydrous methanol (8 ml) was added morpholine (1 ml). After 3 hours thereaction mixture was evaporated on a rotovapor followed by high vacuum.The residue was flash chromatographed (short contact time) on a silicagel column using 5% MeOH in CH₂ Cl₂. The less polar green material wascollected and identified as the title compound (322 mg, 61%). Ananalytical sample was obtained by precipitating it from a solution ofCH₂ Cl₂ and ether with hexane to yield a green amorphous powder.

Anal Calc'd. for C₂₃ H₃₀ N₆ O₆ : C, 56.78; H, 6.22; N, 17.27; Found: C,54.86; H, 6.38; N, 16.18.

IR(KBr, ν_(max), Cm⁻¹): 3440, 3305, 2920, 1675, 1620, 1540, 1445, 1375,1310, 1275, 1060.

UV(MeOH, λ_(max), nm): 386 and 248.

NMR(pyridine d₅, δ): 1.80 (br,m,1H), 2.12(s,3H), 2.74(m,1H), 2.84(s,3H),2.88(s,3H), 3.20(s,3H), 3.20-3.84(m,12H), 4.04 (dd,1H,J=11,4Hz),4.39(d,1H,J=14Hz), 5.04(t,1H), 5.43(dd,1H,J=11, 4Hz), 7.83(s,1H), 8.38(s,1H).

EXAMPLE 2 7-[(Dimethylamino)methylene]amino-N¹⁰-(1-piperidinylmethylene)-9a-methoxymitosane ##STR10##

To a solution of 7-[(dimethylamino)methylene]amino-N¹⁰-(dimethylamino)methylene-9a-methoxymitosane (520 mg, 1.17 mM) inanhydrous methanol was added piperidine (1 ml) and the reaction mixturestirred for 3.75 hours at ca. 22° C. The solvent and excess reagent wereremoved by first evaporating under reduced pressure on a rotovaporfollowed by high vacuum. The residue was flash chromatographed (shortcontact time) on silica gel column employing 5% MeOH in CH₂ Cl₂ as theeluting solvent. The least polar green material was isolated as a greenfoam (131 mg, 23%) and was identified as the title compound. Ananalytical sample was obtained by precipitation from methylenechloride-ether-hexane solvent mixture.

Anal. Calc'd. for C₁₉ H₂₅ N₅ O₅ : C, 59.49; H, 6.66; N, 17.34; Found: C,58.56; H, 6.89; N, 16.20.

IR(KBr, ν_(max), Cm⁻¹): 3440, 2945, 1675, 1610, 1545, 1450, 1375, 1310,1255, 1060.

UV(MeOH, λ_(max), nm): 386 and 246.

NMR (pyridine d₅, δ): 1.32(brs,6H), 1.92(m,1H), 2.12(s,3H),2.76(brs,1H), 2.80(s,3H), 3.16(brs,2H), 3.20(s,3H), 3.60 (m,4H),4.10(dd,1H,J=11, 4Hz), 4.44(d,1H,J=14Hz), 5.08(t,1H),5.50(dd,1H,J=11,4Hz), 7.82(s,1H), 8.46(s,1H).

EXAMPLE 3 7-[(Dimethylamino)methylene]amino-N¹⁰-(4-morpholinyl)methylene-9a-methoxymitosane

To a solution of 7-[(dimethylamino)methylene]amino-9a-methoxymitosane(116 mg, 0.3 mM) in chloroform (5 ml) and methanol (1 ml) was addedmorpholine formamide dimethyl acetal (0.6 ml). The reaction mixture wasstirred at ca. 55° C. (oil bath) for 48 hours. The progress of thereaction was monitored by silica gel thin layer chromatography (10% MeOHin CH₂ Cl₂). At the completion of the reaction, almost all of thestarting material (R_(f) =0.43) was converted to the major greenmaterial (R_(f) =0.57). The reaction mixture was evaporated on arotovapor and the resulting oily residue was chromatographed on aluminacolumn (Woelm, Grade III) using CH₂ Cl₂ (50 ml), 1% MeOH in CH₂ Cl₂ (50ml), then 2% MeOH in CH₂ Cl₂ as eluting solvents. The desired compound(96 mg, R_(f) =0.57) was obtained as an amorphous solid, whose NMRspectrum was identical to the compound described in Example 1.

The following compounds of Formula I wherein A is (CH₃)₂ N--CH═N-- and Bhas the meaning given below may be prepared by substituting theindicated amine for morpholine in Example 1.

EXAMPLE 1 MODIFICATION

    ______________________________________                                        Amine Reactant B of Product                                                   ______________________________________                                        Pyrrolidine                                                                                   ##STR11##                                                     Thiomorpholine                                                                                ##STR12##                                                     Piperazine                                                                                    ##STR13##                                                     Ethyl 1-piperazine- carboxylate                                                               ##STR14##                                                     Azepine                                                                                       ##STR15##                                                     Oxazepine                                                                                     ##STR16##                                                     Thiazepine                                                                                    ##STR17##                                                     1,3-Diazine                                                                                   ##STR18##                                                     1-Methylpiperazine                                                                            ##STR19##                                                     1-Phenylpiperazine                                                                            ##STR20##                                                     ______________________________________                                    

The following amide acetals may be substituted for morpholine formamidedimethyl acetal in the procedure of Example 3 to give the correspondingunsymmetrical bis-amidines of Formula I.

N,N-diisopropylformamide diethylacetal

N,N-Dimethylacetamide dimethylacetal

2,2-Dimethoxy-1-methylpyrrolidine

GENERAL PROCEDURE FOR PREPARING 7-AMIDINO-N¹⁰ -FORMYL-9a-METHOXYMITOSANE

The procedure involves the reaction of a 7-amidino mitomycin Cderivative with an excess of 4-morpholinyl formamide dimethyl acetal inchloroform at approximately 60° C. for 18 to 48 hours as is illustratedin Example 3. When the 7-amidino functionality is 4-morpholinylmethylene the N¹⁰ -formyl compound can be prepared directly frommitomycin C (see Example 4). Thin layer chromatography (silica gel, 10%MeOH in CH₂ Cl₂) of the reaction mixture at the end of the reactionperiod reveals, that all of the starting material is converted to twofaster moving green components. The excess acetal and solvent is removedby evaporation under reduced pressure followed by under high vacuum atapproximately 60° C. When the resulting oily residue is chromatographed(drip method) on silica gel rather than alumina as specified in Example3, degradation to a less polar green material occurs. This is isolatedand characterized as the 7-amidino-N¹⁰ -formyl-9a-methoxymitosanecompound. The N¹⁰ -formyl compounds are usually isolated as minorproducts by this method.

EXAMPLE 4 7-[(Morpholylamino)methylene]amino-N¹⁰-formyl-9a-methoxymitosane ##STR21##

A suspension of mitomycin C (617 mg, 1.85 mM) in chloroform (30 ml) washeated with 4-morpholinyl formamide dimethyl acetal (19.5 ml) at 55° C.for 39 hours. The solvent and excess acetal was removed by evaporationon a rotovapor at 40° C. followed by under high vacuum untilapproximately 5 ml of oily residue was left. The oily residue waschromatographed on silica gel (40 gm) column packed, employing theslurry method and using CH₂ Cl₂. The column was eluted with CH₂ Cl₂ (200ml), 2% MeOH in CH₂ Cl₂ (350 ml) and 5% MeOH in CH₂ Cl₂ (200 ml).Fractions containing the least polar green material were pooled andconcentrated. This material was rechromatographed on silica gel columnpacked with 4% MeOH in CH₂ Cl₂. Elution with the same solvent,collection, and evaporation of the first green band afforded the titlecompound as a dark green amorphous solid (50 mg).

Anal. Calc'd for C₁₉ H₂₃ N₅ O₆ : C, 54.90; H, 5.48; N, 15.24, Found: C,52.00; H, 5.44; N, 13.55.

IR (KBr, ν_(max), cm⁻¹): 3420, 3280, 2910, 1755, 1700, 1620, 1540, 1440,1380, 1305, 1205, 1100, 1060, 1020.

UV (MeOH, λ_(max), nm): 381 and 229.

NMR (pyridine d₅, δ): 2.10(s,3H), 2.14(t,1H,J=8Hz), 2.84 (brs,1H),3.08(brs,1H), 3.26(s,3H), 3.39;(brs, 2H), 3.50-3.80 (m,7H),4.05(dd,1H,J=3Hz), 4.42(d,1H,J=13Hz), 5.15(t,1H, J=13Hz),4.44;(dd,1H,J=3Hz), 7.95(s,1H), 9.45(2,1H), 13.1(brs,1H).

EXAMPLE 5 7-[(Dimethylamino)methylene]amino-N¹⁰-formyl-9a-methoxymitosane ##STR22##

To a solution of 7-[(dimethylamino)methylene]amino-9a-methoxymitosane(379 mg, 0.97 mM) in chloroform was added 4-morpholinyl formamidedimethyl acetal (3.5 ml). The reaction mixture was heated at 55° C. for18 hours. The process of the reaction was monitored by thin layerchromatography (silica gel, 10% MeOH in CH₂ Cl₂. The reaction mixturewas evaporated on a rotovapor at 40° C. followed by under high vacuum at60° C. The oily residue was chromatographed on silica gel column packedusing CH₂ Cl₂. Elution with CH₂ Cl₂ (100 ml), 5% MeOH in CH₂ Cl₂ (300ml) and 10% MeOH in CH₂ Cl₂ (200 ml) afforded two green colored syrups.The faster moving component was rechromatographed on silica gel columnpacked with 5% MeOH in CH₂ Cl₂. Elution with the same solvent (250 ml)followed by with 10% MeOH in CH₂ Cl₂ (250 ml) afforded 40 mg of the lesspolar amorphous solid green material which was characterized as thetitle compound.

Anal. Calc'd for C₁₉ H₂₃ N₃ O₆ : C, 54.63; H, 5.51; N, 16.77 Found: C,54.35; H, 5.30; N, 16.15.

IR (KBr), ν_(max), cm⁻¹): 3460, 3300, 2930, 1765, 1710, 1630, 1550,1440, 1380, 1310, 1210, 1105, 1060.

UV (MeOH, λ_(max), nm): 387 and 233.

NMR (pyridine d₅, δ): 2.14(2,3H), 2.26(t,1H,J=8Hz), 2.82(s,4H),2.90(s,3H), 3.05(brs,1H), 3.28(s,3H), 3.63 (d,1H,J=13Hz),4.04(dd,1H,J=13,3Hz), 4.45(d,1H,J-13Hz), 5.18(t,1H,J=13Hz),5.43(dd,1H,J=13,3Hz), 7.90(s,1H), 9.45(s,1H), 13.14(brs,1H).

ACTIVITY AGAINST P-388 MURINE LEUKEMIA

The following table contains the results of laboratory tests with CDF₁male mice implanted intraperitoneally with a tumor inoculum of 10⁶ascites cells of P-388 murine leukemia and treated with various doses ofeither a test compound of Formula I or mitomycin C. The compounds wereadministered by intraperitoneal injection. Groups of six mice were usedfor each dosage level and they were treated with a single dose of thecompound on day one only. A group of ten saline treated control mice wasincluded in each series of experiments. The mitomycin C treated groupswere included as a positive control. A 30 day protocol was employed withthe mean survival time in days being determined for each group of miceand the number of survivors at the end of the 30 day period being noted.The mice were weighed before treatment and again on day six. The changein weight was taken as a measure of drug toxicity. Mice weighing 20grams each were employed and a loss in weight of up to approximately 2grams were not considered excessive. The results were determined interms of % T/C which is the ratio of the mean survival time of thetreated group to the mean survival time of the saline treated controlgroup times 100. The mean survival time for saline treated controlanimals was nine days. The "maximum effect" in the following table isexpressed as % T/C and the dose giving that effect is given. The valuesin parenthesis are the values obtained with mitomycin C as the positivecontrol in the same experiment. Thus a measure of the relative activityof the present substances to mitomycin C can be estimated. A minimumeffect in terms of % T/C was considered to be 125. The minimum effectivedose reported in the following table is that dose giving a % T/C ofapproximately 125. The two values given in each instance in the "averageweight change" column ware respectively the average weight change permouse at the maximum effective dose and at the minimum effective dose.

    ______________________________________                                        Inhibition of P-388 Murine Leukemia                                                                    Minimum  Average                                     Compound   Maximum Effect                                                                              effective                                                                              weight                                      (Example No.)                                                                            % T/C    dose.sup.1                                                                             dose   change.sup.2                              ______________________________________                                        1          222 (172)                                                                              6.4 (3.2)                                                                              0.1    -0.4; +1.7                                2          194 (172)                                                                              6.4 (3.2)                                                                              0.4    +0.2; +0.6                                4          175 (270)                                                                              3.2 (4.8)                                                                              <0.4   -0.5; +0.3                                5          170 (270)                                                                              3.2 (4.8)                                                                              0.4    -1.4; +1.3                                ______________________________________                                         .sup.1 mg/kg of body weight                                                   .sup.2 grams per mouse, days 1-6, at maximum and minimum effective doses 

Compounds 1 and 2 were similarly found to provide maximum survivalincreases greater than mitomycin C in mice bearing B16 melanomaimplants.

What is claimed is:
 1. A compound having the formula ##STR23## whereinR¹ is hydrogen, lower alkyl, lower alkanoyl, benzoyl or substitutedbenzoyl wherein said substituent is lower alkyl, lower alkoxy, halo,amino, or nitro, andA and B are different and are independently selectedfrom the amidino group having the formula ##STR24## wherein R² ishydrogen, lower alkyl, phenyl, lower alkylphenyl, lower alkoxyphenyl,halophenyl, or aminophenyl, R³ is lower alkyl, or lower alkoxy, R⁴ islower alkyl, or R³ and R⁴ together with the nitrogen atom to which theyare attached constitute pyrrolidine, 2-, or 3-lower alkylpyrrolidine,piperidine, 2-, 3-, or 4-lower alkylpiperidine, 2,6-diloweralkylpiperidine, piperazine, 4-substituted piperazine wherein said4-substituent is alkyl, or carbalkoxy each having 1 to 8 carbon atoms,phenyl, methylphenyl, methoxyphenyl, halophenyl, nitrophenyl, or benzyl,azepine, 2-, 3-, 4-, or 5-lower alkylazepine, morpholine,thiomorpholine, thiomorpholine-1-oxide, or thiomorpholine-1,1-dioxide,or B is the amino formyl group (NHCHO).
 2. The compound of claim 1wherein A and B are the said amidino group in which R² is hydrogen, andR³ and R⁴ are straight chain lower alkyl or, together with the nitrogenatom to which they are attached, constitute pyrrolidine, 2-, or 3-loweralkylpyrrolidine, piperidine, 2-, 3-, or 4-lower alkylpiperidine,2,6-dilower alkylpiperidine, piperazine, 4-substituted piperazinewherein said 4-substituent is alkyl, or carbalkoxy each having 1 to 8carbon atoms, phenyl, methylphenyl, methoxyphenyl, halophenyl,nitrophenyl, or benzyl, azepine, 2-, 3-, 4-, or 5-lower alkylazepine,morpholine, thiomorpholine, thiomorpholine-1-oxide, orthiomorpholine-1,1-dioxide.
 3. The compound of claim 1 wherein A is agroup of the formula ##STR25## wherein R⁵ and R⁶ are straight chainlower alkyl groups and B is a group of the formula ##STR26## wherein R⁷and R⁸ together with the nitrogen to which they are attached constitutepyrrolidine, 2-, or 3-lower alkylpyrrolidine, piperidine, 2-, 3-, or4-lower alkylpiperidine, 2,6-dilower alkylpiperidine, piperazine,4-substituted piperazine wherein said 4-substituent is alkyl, orcarbalkoxy each having 1 to 8 carbon atoms, phenyl, methylphenyl,methoxyphenyl, halophenyl, nitrophenyl, or benzyl, azepine, 2-, 3-, 4-,or 5-lower alkylazepine, morpholine, thiomorpholine,thiomorpholine-1-oxide, or thiomorpholine-1,1-dioxide.
 4. The compoundof claim 3 wherein B is ##STR27##
 5. The compound of claim 3 wherein Bis ##STR28##
 6. The compound of claim 1,[1aS-(1aβ,8β,8aα,8bβ)]-6-[((dimethylamino)methylene)amino]-8-[((1-morpholinemethylene]-aminocarbonyl)oxy)methyl]-1,1a,2,8,8a,8b-hexahydro-8a-methoxy-5-methyl-azirino[2',3':3,4]pyrrolo[1,2-a]indole-4,7-dione.7. The compound of claim 1,[1aS-(1aβ,8β,8aα,8bβ)]-6-[((dimethylamino)methylene)amino]-8-[(((1-piperidinylmethylene)-aminocarbonyl)oxy)methyl]-1,1a,2,8,8a,8b-hexahydro-8a-methoxy-5-methyl-azirino[2',3':3,4]pyrrolo[1,2-a]indole-4,7-dione.8. The method of inhibiting growth of a mammalian tumor which comprisessystemic administration to a mammal bearing a tumor, a substantiallynon-toxic antitumor effective dose of a compound of claim
 1. 9. Thecompound of claim 1 wherein A is the said amidine group and B is theamino formyl (--NHCHO) group. 10.[1aS-(1aβ,8β,8a.alpha.,8bβ)]-6-[((morpholylamino)methylene)-amino]-8-[((formylaminocarbonyl)oxy)methyl]-1,1a,2,8,8a,8b-hexahydro-8a-methoxy-5-methyl-azirino[2',3':3,4]pyrrolo[1,2-a]indole-4,7-dione.11.[1aS-(1aβ,8β,8aα,8bβ)-6-[((dimethylamino)methylene)-amino]-8-[((((formyl)amino)carbonyl)oxy)methyl]-1,1a,2,8,8a,8b-hexahydro-8a-methoxy-5-methyl-azirino[2',3':3,4,]pyrrolo[1,2-a]-indole-4,7-dione.